With the development of science and technology, panel display devices have replaced bulky CRT (Cathode Ray Tube) display devices and have spread into people's everyday life. At present, common panel display devices include LCD (Liquid Crystal Display) and OLED (Organic Light-Emitting Diode) display devices.
During image formation, each pixel dot in the LCD display device and the active matrix OLED (AMOLED) display device is driven by thin film transistors (TFT) integrated in the array substrate to realize image display. Thin film transistors, as control switches, are critical for LCD display devices and OLED display devices in display and are directly related to the development direction of high performance display devices.
As illustrated in FIG. 1A, a thin film transistor comprises a substrate P1 and a gate layer P2 formed on the substrate P1, a gate insulating layer P4, an active layer and respective insulating layer (namely composite layer P5), a source layer P6 and a drain layer P3. At present, source and drain in a thin film transistor are typically disposed in same and one layer, for example, the drain layer P6 and the source layer P3 are formed with a gap or trench therebetween. Accordingly, in a known thin film transistor manufacturing process, the source and drain film layer is formed by a film formation step, and then the source and drain film layer is subjected to exposure, development, and etching steps to form a source and a drain with a gap or trench therebetween. Thus, a source and a drain separated from each other are formed in the same layer.
As illustrated in FIG. 1B, the array substrate comprises the above-mentioned thin film transistors (TFT) and a passivation layer P7, a pixel electrode layer P8, wherein the passivation layer P7 is disposed over the TFTs and further provided with a via P9, the pixel electrode layer P8 is disposed over the passivation layer P7, and the drain layer P3 and the pixel electrode layer P8 of the TFTs are connected with each other through the via P9.
However, being limited by the capabilities of a conventional equipments and processes, a channel (i.e., a conducting region between the source and the drain) is often not completely etched, thus the source and the drain may be bridge connected with each other. As a result, it causes defectiveness of bright spots for pixels, and lowers the product quality grades (for example, grade lowered from P level to S level). Therefore, how to ensure completely disconnection between the source and the drain of a thin film transistor and improve the quality of products has become a problem to be solved in the industry.